Microcell systems for delivering benefit agents

ABSTRACT

A benefit agent delivery system whereby benefit agents can be released over a period of time and/or a variety of different benefit agents can be delivered from the same system and/or different concentrations of benefit agents can be delivered from the same system. The benefit agent delivery system includes a plurality of microcells, wherein the microcells are filled with a formulation comprising a benefit agent and an organic solvent. The microcells include an opening, and the opening is spanned by a porous diffusion layer. Different microcells may be loaded with different benefit agents, thereby providing a mechanism to deliver different, complimentary, or incompatible benefit agents.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 63/107,170, filed on Oct. 29, 2020. The entire contents of any patent, published application, or other published work referenced herein is incorporated by reference.

BACKGROUND

Delivery of benefit agents, such as pharmaceuticals, aromatic compounds and other benefit agents are delivered by a variety of methods. For example, a pharmaceutical agent can be delivered transdermally via a patch. Combinations of aromatic compounds for air care can be delivered via thermal activation of a liquid or via thermal activation of an impregnated porous substrate, etc. Transdermal delivery of pharmaceutical agents has proven effective for drugs that are able to move across the skin barrier. For example, small amounts of nicotine can be delivered over extended periods with transdermal patches that suspend the nicotine in an ethylene vinyl acetate (EVA) copolymer. See, e.g., Nicoderm-CQ® by GlaxoSmithKline (Brentford, UK). Most of the commercially available transdermal patches contain a matrix with only one drug, or a combination of drugs that are compatible for storage, such as oxycodone and tocopherol. See, e.g., TPM/Oxycodone patch from Phosphagenics, Ltd. (Melbourne, AU). Nonetheless, the efficacy of multi-component patches may degrade with time as the components interact. See, e.g., reports of crystallization in rotigotine transdermal patches (Nuepro®, UCB, Inc., Smyrna, Ga.).

Because there are a number of medications or other benefit agents that are best used in combination, there is a need for a simple (and inexpensive) delivery system that allows for the simultaneous delivery of multiple benefit agents and other components from the same delivery system. Additionally, it would be beneficial if the delivery could be accomplished over a period of time and/or on demand.

SUMMARY

The invention addresses these needs by providing a benefit agent delivery system whereby combinations of benefit agents can be delivered from the same device. Additionally, the benefit agent delivery systems of the invention allow for the delivery of incompatible benefit agents at different concentrations and/or different volumes from the same delivery system.

In one aspect, the invention is a benefit agent delivery system that includes a layer of microcells, the layer of microcells comprising: A plurality of a first type of microcells filled with a first formulation comprising a first benefit agent and a carrier, wherein the carrier of the first formulation comprises a first organic solvent; a plurality of a second type of microcells filled with a second formulation comprising a second benefit agent and a carrier, wherein the carrier of the second formulation comprises a second organic solvent, and wherein the first and second benefit agents are different; a plurality of a third type of microcells that do not contain any formulation comprising a benefit agent. Each microcell of the pluralities of the first, second, and third types of microcells includes walls and an opening. Each microcell of the pluralities of the first and second types of microcells includes a sealing layer spanning the opening. At least one microcell of the first type of microcells does not have any adjacent microcell of the second type of microcells in the layer of microcells. The first organic solvent and the second organic solvent may be the same or different. Each of the first type microcells may not have any adjacent second type of microcells in the layer of microcells. At least one of the first type of microcells may be separated from the second type of microcells by two, three or more of the third type of microcells. Each of the first type of microcells may be separated from the second type of microcells by two, three or more of the third type of microcells. The plurality of the third type of microcells may not include a sealing layer spanning the opening. The plurality of the first and second types of microcells may further comprise an adhesive layer adjacent to the sealing layer. The plurality of the first type of microcells may further comprise a first porous diffusion layer adjacent the sealing layer, and the plurality of the second type of microcells further comprises a second porous diffusion layer adjacent to the sealing layer. The first porous diffusion layer may have average pore size that is larger than the average pore size of the second porous diffusion layer.

In one aspect, the benefit agent delivery system includes a layer of microcells, the layer of microcells comprising: A plurality of a first type of microcells filled with a first formulation comprising a first benefit agent and a carrier, wherein the carrier of the first formulation comprises a first organic solvent; a plurality of a third type of microcells filled with a third formulation that does not contain any benefit agent. Each microcell of the first and third types includes walls and an opening. Each microcell of the first and third types includes a sealing layer spanning the opening. The benefit agent delivery system comprises one or more segments of the first type of microcells, wherein each segment of the first type of microcells exclusively comprises only microcells of the first type of microcells, and wherein all the microcells of the first type of microcells that are adjacent to any other microcell of the segment of the first type of microcells are members of the same segment. The periphery of at least one segment of the first type of microcells is surrounded by microcells of the third type of microcells. The benefit agent delivery system may further comprise a plurality of a second type of microcells filled with a second formulation comprising a second benefit agent and a carrier, wherein the carrier of the second formulation comprises a second organic solvent. Each microcell of the second type includes walls and an opening, wherein each microcell of the second type includes a sealing layer spanning the opening. The benefit agent delivery system may comprise one or more segments of the second type of microcells, wherein each segment of the second type of microcells exclusively comprises only microcells of the second type of microcells, and all the microcells of the second type of microcells that are adjacent to any other microcell of the segment of the second type of microcells are members of the same segment. The periphery of at least one segment of the second type of microcells may be surrounded by microcells of the third type of microcells. The first organic solvent may be the same or different from the second organic solvent. Each of the first type microcells may not have any adjacent second type of microcells in the layer of microcells. Each of the plurality of the first, second, and third types of microcells may further comprise a porous diffusion layer adjacent to the sealing layer. Each of the plurality of the first, second, and third types of microcells may further comprise an adhesive layer, wherein the porous diffusion layer is disposed between the sealing layer and the adhesive layer.

The benefit agent delivery system may be used for transdermal delivery of a benefit agent or for delivery of a benefit agent in any other location.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a benefit agent delivery system including a plurality of first, second, and third types of microcells;

FIGS. 2A and 2B illustrate an embodiment of a benefit agent delivery system including a plurality of first, second, and third types of microcells comprising two different benefit agents;

FIG. 2C illustrates an embodiment of a benefit agent delivery system including a plurality of first, second, and third types of microcells viewed from above;

FIG. 2D illustrates an embodiment of a benefit agent delivery system including a plurality of first, second, and third types of microcells including a porous diffusion layer wherein the opening to different microcells is spanned by porous diffusion layers having different average pore sizes;

FIG. 3 illustrates an embodiment of a benefit agent delivery system including two segments of the first type of microcells, both of which are surrounded by microcells of the third type of microcells;

FIG. 4 shows a method for making microcells for the invention using a roll-to-roll process;

FIGS. 5A and 5B detail the production of microcells for a benefit agent delivery system using photolithographic exposure through a photomask of a conductor film coated with a thermoset precursor;

FIGS. 5C and 5D detail an alternate embodiment in which microcells for a benefit agent delivery system are fabricated using photolithography. In FIGS. 5C and 5D a combination of top and bottom exposure is used, allowing the walls in one lateral direction to be cured by top photomask exposure, and the walls in another lateral direction to be cured bottom exposure through the opaque base conductor film;

FIGS. 6A-6D illustrate the steps of filling and sealing an array of microcells to be used in a benefit agent delivery system;

FIG. 7A illustrates a photograph of a system for delivering fragrances;

FIG. 7B illustrates a benefit agent delivery system having a segment of microcells that do not contain any formulation.

DETAILED DESCRIPTION

The invention provides a benefit agent delivery system whereby benefit agents can be released over time and/or a variety of different benefit agents can be delivered from the same system and/or different concentrations of benefit agents can be delivered from the same system. The invention is well suited for delivering pharmaceuticals to patients transdermally. However, the invention may be used to deliver benefit agents on surfaces and in spaces, generally. For example, the invention can deliver tranquilizing agents to a horse during transport. The benefit agent delivery system includes a plurality of microcells, wherein the microcells are filled with a medium including benefit agents. The microcells include an opening, the opening being spanned by a porous diffusion layer. The microcell arrays may be loaded with different benefit agents and other ingredients, thereby providing a mechanism to deliver different, or complimentary, benefit agents and other ingredients on demand and over a period of time. A porous diffusion layer may be present adjacent to the sealing layer.

The benefit agent delivery systems can also be incorporated into the structural walls of smart packing. Such delivery systems makes it possible to have long term release of antioxidants into a package containing fresh vegetables. This “smart” packaging will dramatically improve the shelf life of certain foods or other items, and it will only require the amount of antioxidant necessary to maintain freshness until the package is opened. Thus, the same packaging can be used for items that is distributed locally, across the country, or around the globe. The benefit agent delivery system may also delivery benefit agents in many other uses via a film, such as on aromatic materials (air care), anti-microbial compounds on surfaces, etc.

The term “benefit agent” includes a pharmaceutical, cosmetic, aromatic, anti-microbial, anti-oxidant, and other benefit agents. It also includes agents that enhance, activate or improve the effectiveness or efficiency of the benefit agent.

The term “segment of the first type of microcells” means a set of microcells that comprises exclusively microcells the first type of microcells, and all the microcells of the first type of microcells that are adjacent to any other microcell of the segment of the first type of microcells are members of the same segment. Analogously, the terms “segment of the second type of microcells”, “segment of the third type of microcells” and so on, are defined. That is, a segment is a set of microcells of the A type of microcells that occupy an area, wherein all of the microcells in the area are of the same (A) type of microcells and there are no microcells that are adjacent to any of the microcell of the segment that are of the A type that are not part of the segment.

The term “adjacent microcells” refers to microcells of the benefit agent delivery system that share a wall. That is, adjacent microcells are microcells that are next to each other.

The term “porous diffusion layer” includes any film that has average pores from 0.1 nm to 100 μm.

The term “filled” in reference to a microcell (or microcells) mean that a formulation is present in the microcell (or microcells). It does not necessarily mean that the whole volume of the microcell is occupied by the formulation. In other words, the term “filled” in reference to a microcell (or microcells) include the concepts of a partially filled microcell (or microcells) as well as a completely “filled” microcell (or microcells). Analogously, the tern “filling” in reference to a microcell (or microcells) means that a formulation is added into a microcell (or microcells). It does not necessarily mean that sufficient amount of the formulation is being added into the microcell to occupy its entire volume.

The invention also provides a system for simple and low cost delivery of combinations of benefit agents over a period of time. Such a delivery system may be used, for example, as an emergency delivery system for a person undergoing an allergic reaction. The system may include epinephrine, as well as antihistamines. The device can be applied and then triggered to cause the benefit agents to be quickly passed through the skin. The system may be particularly effective as a back-up system for small children who may be exposed to life-threatening allergens while on a field trip, etc. A parent can affix the delivery system to the child with instructions to activate the device in the event of, e.g., a bee sting. Because the device is relatively simple, compliance with proper delivery protocols will be greater than, e.g., an epipen.

In one embodiment, the benefit agent delivery system includes a layer of microcells. The layer of microcells comprises a plurality of a first type of microcells filled with a first formulation comprising a first benefit agent and a carrier. The carrier of the first formulation is a first organic solvent. The layer of microcells also comprises a plurality of a second type of microcells filled with a second formulation comprising a second benefit agent and a carrier. The carrier of the second formulation is a second organic solvent. The layer of microcells also comprises a plurality of third type of microcells. The plurality of a third type of microcells do not contain any benefit agent formulation. Each of the first type microcells does not have any adjacent second type of microcells in the layer of microcells.

An overview of a benefit agent delivery system is shown in FIG. 1. The system includes a plurality of a first type of microcells 11A, a plurality of a second type of microcells 11B, and a plurality of a third type of microcells 11C. Each microcell of the first and second types includes a medium (also called internal phase), that includes benefit agents. Each microcell of the first and second types includes a wall 14 and an opening; the opening is sealed with a sealing layer 15. The sealing layer 15 may be constructed from, for example, methylcellulose, hydroxymethylcellulose, an acrylate, a methacrylate, a polycarbonate, a polyvinyl alcohol, cellulose, poly(N-isopropylacrylamide) (PNIPAAm), poly(lactic-co-glycolic acid) (PLGA), polyvinylidene chloride, acrylonitrile, amorphous nylon, oriented polyester, terephthalate, polyvinyl chloride, polyethylene, polypropylene, polybutylene, polyisobutylene, or polystyrene. The benefit agent delivery system may additionally include an adhesive layer 16, which may include, for example, a polyisobutylene, an acrylic, a poly(ethylene)glycol, or a silicone. The sealing and adhesive layers are porous. The microcells of the first type 11A and the microcells of the second type 11B are separated by a microcell of a third type 11C, which does not contain any formulation comprising a benefit agent. As shown in FIG. 1, there is no sealing layer in the opening of the microcell of the third type 11C. The material of the sealing composition 15A has been deposited on the side of the microcell that is opposite to the opening of the microcell 11C. In the case of the first and second types of microcells, the sealing composition is applied on microcells that are filled with formulations comprising benefit agents. Thus, the sealing composition is formed on the opening of each individual microcells of the first and second type as shown in FIG. 1 (or above it as a common sealing film). In the case of the microcells of the third type that do not contain a formulation comprising a benefit agent, the applied sealing composition is deposited on side of the microcell that is opposite to the opening side. The benefit agents included in microcells 11A and 11B are delivered from the benefit agent delivery system through sealing layer 15 and adhesive layer 16. The release direction 17 of the benefit agents is shown in FIG. 1 by an arrow.

As shown in FIG. 2A, a first microcell 11 a may include a first benefit agent 12 a in a carrier that comprises a first organic solvent, while a second microcell 11 b includes a second benefit agent 12 b in a carrier that comprises a second organic solvent, while a third microcell 11 c is located in-between microcell 11 a and 11 b and it does not include any formulation comprising a benefit agent. In another example, the first type of microcells may be filled with a first benefit agent without any carrier and/or the second type of microcells may be filled with a second benefit agent without any carrier. Each microcell is part of an array that is formed from a polymer matrix, which is described in more detail below. The benefit agent delivery system will typically include a backing barrier 13 to provide structural support and protection against moisture ingress and physical interactions. The microcells are defined by walls 14 that are at least 1 μm high, although they can be much higher depending upon the desired depth of the microcell. The microcells may be arranged as squares, a honeycomb, circles, etc. Microcells 11 a and 11 b comprise a porous sealing layer 15. Often microcells additionally include an adhesive layer 16 that is also porous to the benefit agent. The adhesive layer 16 assists in keeping the benefit agent delivery system adjacent to a surface. As explained above, the sealing composition of the microcell of the third type 11 c is deposited at the surface opposite to the side of the opening.

FIG. 2B illustrates an example of a benefit agent delivery system of the present invention, wherein the microcells of the second type of microcells 11 d have smaller volume than the microcells of the first type of microcells 11 a. Other practical options exist, wherein the microcells of the second type of microcells are present in the benefit agent delivery system having various volumes. The same can be true for the microcells of the first type of microcells and for the microcells of the third type of microcells. Such variations may provide additional control of delivering benefit agents over a period of time and on specific areas or spaces.

FIG. 2C illustrates a similar system of microcells as of FIG. 2A viewed from above. A plurality of the first type microcells are separated from a plurality of the second type of microcells by a plurality of the third type of microcells, which do not contain any formulation comprising a benefit agent.

The benefit agent delivery system may also include a porous diffusion layer, which may be constructed from a variety of natural or non-natural polymers, such as acrylates, methacrylates, polycarbonates, polyvinyl alcohols, cellulose, poly(N-isopropylacrylamide) (PNIPAAm), poly(lactic-co-glycolic acid) (PLGA), polyvinylidene chloride, acrylonitrile, amorphous nylon, oriented polyester, terephthalate, polyvinyl chloride, polyethylene, polypropylene, polybutylene, polyisobutylene, or polystyrene. Using picoliter injection with inkjet or other fluidic systems, individual microcells can be filled to enable a variety of different benefit agents to be included in a benefit agent delivery system.

FIG. 2D shows another embodiment of a benefit agent delivery system in which the porosity of the diffusion layer is varied for different microcells. This can be accomplished by using different polymer materials and microinjection, e.g., using inkjet during the sealing process (described below). Such systems allow a single delivery system to administer varying concentrations of the same or different benefit agents over a period of time. For example, a system of the invention may include three microcells 37, 38, 39. Microcell 38 does not contain any formulation comprising a benefit agent, whereas microcells 37 and 39 comprise formulations comprising a benefit agent at two different concentrations. However, the dosage time will be controlled by the porosity of the diffusion layer. For example, shortly after application the most concentrated dose may be delivered via microcell 37 via the most porous diffusion layer 34, followed by a less concentrated dose delivered from microcell 39 via the second diffusion layer 35. As described above, the sealing composition and the composition that forms the porous diffusion layer 34 a are deposited on the opposite side of the opening side in the microcell 34 a, which is a microcell of the third type of microcell. FIG. 2D shows example of a benefit agent delivery system wherein the sealing layers 15 of the first and second types of microcells 37 and 39 are located below the surface of the opening of the microcells, that is, inside the microcells. The porous diffusion layers 34 and 35, which are adjacent to the sealing layers, may also be located below the surface of the opening of the microcells, that is, inside the microcells. However, in a different benefit agent delivery system of the present invention, the sealing layers and the porous diffusion layers may be above the surface of the opening of the microcells, that is, outside of the microcells, as common films. In another example, the benefit agent delivery system may comprise microcells of the first and second types, wherein the sealing layers are inside the microcells and the porous diffusion layers are outside the microcells. Furthermore, the adhesive layer 16 is optionally present.

The first type of microcells may be present in the benefit agent delivery system as one segment of the first type of microcells. The second type of microcells may also be present in the benefit agent delivery system as one segment of the second type of microcells. The segment of the first type of microcells may be separated from the segment of the second type of microcell by a segment of the third type of microcells. In other embodiments of the present invention, the first type of microcells occurs in the benefit agent delivery system as two, three or more segments, and the second type of microcells also occur in the system as two, three or more segments, and each of the first type of microcells does not have any adjacent microcell of the second type of microcells. Each of the first type of microcells may be separated by any microcell of the second type of microcells by at least one microcell of the third type of microcells. Alternatively, each of the first type of microcells may be separated by any microcell of the second type of microcells by at least two, three, four, five, or more microcells of the third type of microcells.

A variety of combinations of benefit agents is possible. Microcells might include pharmaceuticals, nutraceuticals, adjuvants, vitamins, or vaccines. Furthermore, the arrangement of the microcells may not be distributed. Rather, the microcells may be filled in clusters, which makes filling and sealing more straightforward. In other embodiments, smaller microcell arrays may be filled with the same medium, i.e., having the same benefit agent at the same concentration, and then the smaller arrays assembled into a larger array to make a delivery system of the invention. In other embodiments, differing porosity can be used with differing contents for a microcell. For example, one microcell may include a solution of enzymes and require a porous diffusion layer that has pores large enough for the enzymes to pass, while an adjacent microcell may include a substrate to activate the enzyme, but require a porous diffusion layer with much smaller pores to regulate delivery of the substrate

In another embodiment, the benefit agent delivery system comprises a first type of microcells and a third type of microcells. The first type of microcells are filled with a first formulation comprising a first benefit agent. The third type of microcells are filled with a formulation that does not contain any benefit agents. Both formulations may comprise an organic solvent. The benefit agent delivery system may contain two, three, or more segments of the first type of microcells and two, three, or more segments of the third type of microcells. At least one of the segments of the first type of microcells is surrounded by microcells of the third type of microcells. An example of such a system is illustrated in FIG. 3, which shows a benefit agent delivery system having two segments of the first type of microcells, both of which are surrounded by microcells of the third type of microcells. FIG. 3 shows a system having one segment of the third types of microcells. This benefit agent delivery system is useful for providing a controlled dose of a benefit agent for transdermal delivery. For example, if a benefit agent that is present in the first type of microcells is an irritant, the separation of the first type of microcells with microcells of the third type microcells that do not contain a benefit agent mitigates the irritation.

The benefit agent delivery system of this embodiment, wherein the third type of microcell comprises a formulation without a benefit agent, may comprise, in addition to the first and third types of microcells, a second type of microcells filled with a second formulation comprising a second benefit agent and a carrier. The carrier may comprise an organic solvent. The benefit agent delivery system may contain two, three, or more segments of the second type of microcells and one, two, three, or more segments of the third type of microcells. At least one of the segments of the first type of microcells is surrounded by microcells of the third type of microcells. Each of the first type of microcells does not have any adjacent second type of microcells in the layer of microcells of the benefit agent delivery system.

In this embodiment, the first, second and third types of microcell comprise an opening and a sealing layer spanning the opening. The first, second and third types of microcell may also comprises a first, second and third porous diffusion layer, respectively, adjacent to the sealing layer. The first, second and third types of microcell may also comprises an adhesive layer adjacent to the sealing layer or adjacent to the first, second, and third porous diffusion layer. The sealing layer may be formed inside each microcell or it may be formed outside the microcell adjacent to each microcell opening. In both cases, the sealing layer may be designed to be different for each microcell type. The same is true for the porous diffusion layer. In other words, the porosity of the sealing layer and/or porous diffusion layer may be different for each type of microcell. This provides an additional control of the amount of each benefit agent that is delivered from the system. One way to control the porosity is by the average porous size. Another way to control the porosity is by the thickness of each of the layers (sealing layer, porous diffusion layer, and adhesive layer). It is also possible to use different materials for the construction of these layers of the different types of microcells in the same system.

The benefit agent delivery system of the present invention enables the delivery of a combination of benefit agents that are not compatible with each other. For example, if the first benefit agent is not compatible with the second benefit agent and one of both of them degrade in the presence of the other and a first type of microcell is adjacent to a second type of microcell, the two benefit agents may contact each other after they exit the microcell, as they diffuse through the porous adhesive layer and/or the porous diffusion layer, and before they are delivered outside the benefit agent delivery system. Appropriate separation of the first type of microcell from the second type of microcell by one or more third type of microcells mitigates the potential degradation problem.

Each of the microcells includes walls and an opening. The microcells may be square, round, or polygonal, such as a honeycomb structure. For each first and second types of microcell, the opening is spanned the sealing layer. The sealing layer may be constructed from a variety of materials, such as methylcellulose, hydroxymethylcellulose, an acrylate, a methacrylate, a polycarbonate, a polyvinyl alcohol, cellulose, poly(N-isopropylacrylamide) (PNIPAAm), poly(lactic-co-glycolic acid) (PLGA), polyvinylidene chloride, acrylonitrile, amorphous nylon, oriented polyester, terephthalate, polyvinyl chloride, polyethylene, polypropylene, polybutylene, polyisobutylene, or polystyrene.

Techniques for constructing microcells. Microcells may be formed either in a batchwise process or in a continuous roll-to-roll process as disclosed in U.S. Pat. No. 6,933,098. The latter offers a continuous, low cost, high throughput manufacturing technology for production of compartments for use in a variety of applications including benefit agent delivery and electrophoretic displays. Microcell arrays suitable for use with the invention can be created with microembossing, as illustrated in FIG. 4. A male mold 20 may be placed either above the web 24, as shown in FIG. 4, or below the web 24 (not shown); however, alternative arrangements are possible. See U.S. Pat. No. 7,715,088, which is incorporated herein by reference in its entirety. A conductive substrate may be constructed by forming a conductor film 21 on polymer substrate that becomes the backing for a device. A composition comprising a thermoplastic, thermoset, or a precursor thereof 22 is then coated on the conductor film. The thermoplastic or thermoset precursor layer is embossed at a temperature higher than the glass transition temperature of the thermoplastics or thermoset precursor layer by the male mold in the form of a roller, plate or belt.

The thermoplastic or thermoset precursor for the preparation of the microcells may be multifunctional acrylate or methacrylate, vinyl ether, epoxide and oligomers or polymers thereof, and the like. A combination of multifunctional epoxide and multifunctional acrylate is also very useful to achieve desirable physico-mechanical properties. A crosslinkable oligomer imparting flexibility, such as urethane acrylate or polyester acrylate, may be added to improve the flexure resistance of the embossed microcells. The composition may contain polymer, oligomer, monomer and additives or only oligomer, monomer and additives. The glass transition temperatures (or T_(g)) for this class of materials usually range from about −70° C. to about 150° C., preferably from about −20° C. to about 50° C. The microembossing process is typically carried out at a temperature higher than the T_(g). A heated male mold or a heated housing substrate against which the mold presses may be used to control the microembossing temperature and pressure.

As shown in FIG. 4, the mold is released during or after the precursor layer is hardened to reveal an array of microcells 23. The hardening of the precursor layer may be accomplished by cooling, solvent evaporation, cross-linking by radiation, heat or moisture. If the curing of the thermoset precursor is accomplished by UV radiation, UV may radiate onto the transparent conductor film from the bottom or the top of the web as shown in the two figures. Alternatively, UV lamps may be placed inside the mold. In this case, the mold must be transparent to allow the UV light to radiate through the pre-patterned male mold on to the thermoset precursor layer. A male mold may be prepared by any appropriate method, such as a diamond turn process or a photoresist process followed by either etching or electroplating. A master template for the male mold may be manufactured by any appropriate method, such as electroplating. With electroplating, a glass base is sputtered with a thin layer (typically 3000 Å) of a seed metal such as chrome inconel. The mold is then coated with a layer of photoresist and exposed to UV. A mask is placed between the UV and the layer of photoresist. The exposed areas of the photoresist become hardened. The unexposed areas are then removed by washing them with an appropriate solvent. The remaining hardened photoresist is dried and sputtered again with a thin layer of seed metal. The master is then ready for electroforming. A typical material used for electroforming is nickel cobalt. Alternatively, the master can be made of nickel by electroforming or electroless nickel deposition. The floor of the mold is typically between about 50 to 400 microns. The master can also be made using other microengineering techniques including e-beam writing, dry etching, chemical etching, laser writing or laser interference as described in “Replication techniques for micro-optics”, SPIE Proc. Vol. 3099, pp. 76-82 (1997). Alternatively, the mold can be made by photomachining using plastics, ceramics or metals.

Prior to applying a UV curable resin composition, the mold may be treated with a mold release to aid in the demolding process. The UV curable resin may be degassed prior to dispensing and may optionally contain a solvent. The solvent, if present, readily evaporates. The UV curable resin is dispensed by any appropriate means such as, coating, dipping, pouring or the like, over the male mold. The dispenser may be moving or stationary. A conductor film is overlaid the UV curable resin. Pressure may be applied, if necessary, to ensure proper bonding between the resin and the plastic and to control the thickness of the floor of the microcells. The pressure may be applied using a laminating roller, vacuum molding, press device or any other like means. If the male mold is metallic and opaque, the plastic substrate is typically transparent to the actinic radiation used to cure the resin. Conversely, the male mold can be transparent and the plastic substrate can be opaque to the actinic radiation. To obtain good transfer of the molded features onto the transfer sheet, the conductor film needs to have good adhesion to the UV curable resin, which should have a good release property against the mold surface.

Photolithography. Microcells can also be produced using photolithography. Photolithographic processes for fabricating a microcell array are illustrated in FIGS. 5A and 5B. As shown in FIGS. 5A and 5B, the microcell array 40 may be prepared by exposure of a radiation curable material 41 a coated by known methods onto a conductor electrode film 42 to UV light (or alternatively other forms of radiation, electron beams and the like) through a mask 46 to form walls 41 b corresponding to the image projected through the mask 46. The base conductor film 42 is preferably mounted on a supportive substrate base web 43, which may comprise a plastic material.

In the photomask 46 in FIG. 5A, the dark squares 44 represent the opaque area and the space between the dark squares represents the transparent area 45 of the mask 46. The UV radiates through the transparent area 45 onto the radiation curable material 41 a. The exposure is preferably performed directly onto the radiation curable material 41 a, i.e., the UV does not pass through the substrate 43 or base conductor 42 (top exposure). For this reason, neither the substrate 43, nor the conductor 42, needs to be transparent to the UV or other radiation wavelengths employed.

As shown in FIG. 5B, the exposed areas 41 b become hardened and the unexposed areas (protected by the opaque area 44 of the mask 46) are then removed by an appropriate solvent or developer to form the microcells 47. The solvent or developer is selected from those commonly used for dissolving or reducing the viscosity of radiation curable materials such as methylethylketone (MEK), toluene, acetone, isopropanol or the like. The preparation of the microcells may be similarly accomplished by placing a photomask underneath the conductor film/substrate support web and in this case the UV light radiates through the photomask from the bottom and the substrate needs to be transparent to radiation.

Imagewise Exposure. Still another alternative method for the preparation of the microcell array of the invention by imagewise exposure is illustrated in FIGS. 5C and 5D. When opaque conductor lines are used, the conductor lines can be used as the photomask for the exposure from the bottom. Durable microcell walls are formed by additional exposure from the top through a second photomask having opaque lines perpendicular to the conductor lines. FIG. 5C illustrates the use of both the top and bottom exposure principles to produce the microcell array 50 of the invention. The base conductor film 52 is opaque and line-patterned. The radiation curable material 51 a, which is coated on the base conductor 52 and substrate 53, is exposed from the bottom through the conductor line pattern 52, which serves as the first photomask. A second exposure is performed from the “top” side through the second photomask 56 having a line pattern perpendicular to the conductor lines 52. The spaces 55 between the lines 54 are substantially transparent to the UV light. In this process, the wall material 51 b is cured from the bottom up in one lateral orientation, and cured from the top down in the perpendicular direction, joining to form an integral microcell 57. As shown in FIG. 5D, the unexposed area is then removed by a solvent or developer as described above to reveal the microcells 57. The technique described in FIGS. 5C and 5D thus allow the different walls to be constructed with different porosity, as needed for the embodiment illustrated in FIG. 3.

The microcells may be constructed from thermoplastic elastomers, which have good compatibility with the microcells and do not interact with the electrophoretic media. Examples of useful thermoplastic elastomers include ABA, and (AB)n type of di-block, tri-block, and multi-block copolymers wherein A is styrene, α-methylstyrene, ethylene, propylene or norbonene; B is butadiene, isoprene, ethylene, propylene, butylene, dimethylsiloxane or propylene sulfide; and A and B cannot be the same in the formula. The number, n, is ≥1, preferably 1-10. Particularly useful are di-block or tri-block copolymers of styrene or ox-methylstyrene such as SB (poly(styrene-b-butadiene)), SBS (poly(styrene-b-butadiene-b-styrene)), SIS (poly(styrene-b-isoprene-b-styrene)), SEBS poly(styrene-b-ethylene/butylenes-b-stylene)) poly(styrene-b-dimethylsiloxane-b-styrene), poly((α-methylstyrene-b-isoprene), poly(α-methylstyrene-b-isoprene-b-α-methylstyrene), poly(α-methylstyrene-b-propylene sulfide-b-α-methylstyrene), poly(α-methylstyrene-b-dimethylsiloxane-b-α-methylstyrene). Commercially available styrene block copolymers such as Kraton D and G series (from Kraton Polymer, Houston, Tex.) are particularly useful. Crystalline rubbers such as poly(ethylene-co-propylene-co-5-methylene-2-norbomene) or EPDM (ethylene-propylene-diene terpolymer) rubbers such as Vistalon 6505 (from Exxon Mobil, Houston, Tex.) and their grafted copolymers have also been found very useful.

The thermoplastic elastomers may be dissolved in a solvent or solvent mixture, which is immiscible with the display fluid in the microcells and exhibits a specific gravity less than that of the display fluid. Low surface tension solvents are preferred for the overcoating composition because of their better wetting properties over the microcell walls and the electrophoretic fluid. Solvents or solvent mixtures having a surface tension lower than 35 dyne/cm are preferred. A surface tension of lower than 30 dyne/cm is more preferred. Suitable solvents include alkanes (preferably C₆₋₁₂ alkanes such as heptane, octane or Isopar solvents from Exxon Chemical Company, nonane, decane and their isomers), cycloalkanes (preferably C₆₋₁₂ cycloalkanes such as cyclohexane and decalin and the like), akylbezenes (preferably mono- or di-C₁₋₆alkyl benzenes such as toluene, xylene and the like), alkyl esters (preferably C₂₋₅ alkyl esters such as ethyl acetate, isobutyl acetate and the like) and C₃₋₅ alkyl alcohols (such as isopropanol and the like and their isomers). Mixtures of alkyl benzene and alkane are particularly useful.

In addition to polymer additives, the polymer mixtures may also include wetting agents (surfactants). Wetting agents (such as the FC surfactants from 3M Company, Zonyl fluorosurfactants from DuPont, fluoroacrylates, fluoromethacrylates, fluoro-substituted long chain alcohols, perfluoro-substituted long chain carboxylic acids and their derivatives, and Silwet silicone surfactants from OSi, Greenwich, Conn.) may also be included in the composition to improve the adhesion of the sealant to the microcells and provide a more flexible coating process. Other ingredients including crosslinking agents (e.g., bisazides such as 4,4′-diazidodiphenylmethane and 2,6-di-(4′-azidobenzal)-4-methylcyclohexanone), vulcanizers (e.g., 2-benzothiazolyl disulfide and tetramethylthiuram disulfide), multifunctional monomers or oligomers (e.g., hexanediol, diacrylates, trimethylolpropane, triacrylate, divinylbenzene, diallylphthalene), thermal initiators (e.g., dilauroryl peroxide, benzoyl peroxide) and photoinitiators (e.g., isopropyl thioxanthone (ITX), Irgacure 651 Irgacure 369 from Ciba-Geigy) are also highly useful to enhance the physico-mechanical properties of the sealing layer by crosslinking or polymerization reactions during or after the overcoating process.

After the microcells are produced, they are filled with appropriate mixtures of benefit agents. The microcell array 60 may be prepared by any of the methods described above. As shown in cross-section in FIGS. 6A-6D, the microcell walls 61 extend upward from the substrate 63 to form the open cells. The microcells may include a primer layer 62 to passivate the mixture and keep the microcell material from interacting with the mixture containing the benefit agents 65. Prior to filling, the microcell array 60 may be cleaned and sterilized to assure that the benefit agents are not compromised prior to use.

The microcells are next filled with a mixture 64 including benefit agents 65. As shown in FIG. 6B, different microcells may include different benefit agents. The microcells 60 are preferably partially filled to prevent overflow and the unintentional mixing of benefit agents. In systems for delivering hydrophobic benefit agents, the mixture may be based upon a biocompatible oil or some other biocompatible hydrophobic carrier. For example, the mixture may comprise a vegetable, fruit, or nut oil. In other embodiments, silicone oils may be used. The mixture need not be a liquid, however, as gels and other matrices may be suitable to deliver the benefit agent 65.

The microcells may be filled using a variety of techniques. In some embodiments, where a large number of neighboring microcells are to be filled with an identical mixture, blade coating may be used to fill the microcells to the depth of the microcell walls 61. In other embodiments, where a variety of different mixtures are to be filled in a variety of nearby microcell, inkjet-type microinjection can be used to fill the microcells. In yet other embodiments, microneedle arrays may be used to fill an array of microcells with the correct mixtures. The filling may be done in a one-step, or a multistep process. For example, all of the cells may be partially filled with an amount of solvent. The partially filled microcells are then filled with a second mixture including the one or more benefit agents to be delivered.

As shown in FIG. 6C, after filling, the microcells are sealed by applying a polymer 66 that becomes the porous diffusion layer. In some embodiments, the sealing process may involve exposure to heat, dry hot air, or UV radiation. In most embodiments, the polymer 66 will be compatible with the mixture 64, but not dissolved by the solvent of the mixture 64. The polymer 66 will also be biocompatible and selected to adhere to the sides or tops of the microcell walls 61. A suitable biocompatible adhesive for the porous diffusion layer is a phenethylamine mixture, such as described in U.S. patent application. Ser. No. 15/336,841, filed Oct. 30, 2016 and titled “Method for Sealing Microcell Containers with Phenethylamine Mixtures,” which is incorporated herein by reference in its entirety. Accordingly, the final microcell structure is mostly impervious to leaks and able to withstand flexing without delamination of the porous diffusion layer.

In alternate embodiments, a variety of individual microcells may be filled with the desired mixture by using iterative photolithography. The process typically includes coating an array of empty microcells with a layer of positively working photoresist, selectively opening a certain number of the microcells by imagewise exposing the positive photoresist, followed by developing the photoresist, filling the opened microcells with the desired mixture, and sealing the filled microcells by a sealing process. These steps may be repeated to create sealed microcells filled with other mixtures. This procedure allows for the formation of large sheets of microcells having the desired ratio of mixtures or concentrations.

After the microcells 60 are filled, the sealed array may be laminated with a finishing layer 68 that is also porous to the benefit agents, preferably by pre-coating the finishing layer 68 with an adhesive layer, which may be a pressure sensitive adhesive, a hot melt adhesive, or a heat, moisture, or radiation curable adhesive. The laminate adhesive may be post-cured by radiation such as UV through the top conductor film if the latter is transparent to the radiation. In some embodiments, a biocompatible adhesive 67 is then laminated to the assembly. The biocompatible adhesive 67 will allow benefit agents to pass through while keeping the device mobile on a user. Suitable biocompatible adhesives are available from 3M (Minneapolis, Minn.)

Once the benefit agent delivery system has been constructed, it may be covered with an encapsulating covering to provide protection against physical shock. The encapsulating covering may also include adhesives to make sure that the benefit agent delivery system stays affixed, e.g., to a patient's back. The encapsulating covering may also include aesthetic coloring or fun designs for children.

EXAMPLE 1: Benefit Agent Delivery System for Delivery of Perfumes

A benefit agent delivery system 70 was constructed via the embossing process using polyacrylate thermoset material. Each microcell is approximately 130 μm long. The benefit agent delivery system 70 is shown in the photograph of FIG. 7A. An illustration of a side view of the benefit delivery system is provided in FIG. 7B; this drawing is not in scale in terms of the dimensions of the microcells as well as the relative number of microcells of the three segments. A first solution, comprising 20 weight percent of methyl salicylate fragrance ingredient in triethyl citrate carrier by weight of the first solution, was added into a first segment 71 of the microcells covering an area of approximately 3 cm×9 cm of the microcell film. The first solution also contained red food dye to create a visual contrast effect. A second solution, comprising 20 weight percent of isobutyl quinolone fragrance ingredient in triethyl citrate carrier by weight of the second solution, was added into a second segment 72 of the constructed microcells covering an area of approximately 3 cm×9 cm of the microcell film. The two segments are separated by a third segment 73 of microcells that do not contain any formulation. The third segment covered an area of approximately 1 cm×9 cm, as shown in FIG. 7A. An aqueous polymeric composition was applied on the opening side of the three segments of the microcells to seal the first and the second segments of the microcells. As the third segment did not contain any formulation, the sealing composition coated the surface of the empty microcells that is opposite to the opening side, as shown in FIG. 7B. Upon drying, sealing layer 75 is formed on the first and second segments having a thickness of 15 μm. The release of the perfume ingredients from the first and second segments took place over a period of time. This was observed by the characteristic odor of the ingredients, which were detected both immediately after the preparation of the benefit agent delivery system and at least 2 days after the preparation.

Thus, the invention provides for a benefit agent delivery system including a plurality of microcells. The microcells may include differing, non-compatible benefit agents, or differing concentrations of benefit agents. The microcells include an opening that is spanned by a porous diffusion layer. This disclosure is not limiting, and other modifications to the invention, not described, but self-evident to one of skill in the art, are to be included in the scope of the invention. 

1. A benefit agent delivery system including a layer of microcells, the layer of microcells comprising: a plurality of a first type of microcells filled with a first formulation comprising a first benefit agent in a carrier, wherein the carrier of the first formulation comprises a first organic solvent; a plurality of a second type of microcells filled with a second formulation comprising a second benefit agent in a carrier, wherein the carrier of the second formulation comprises a second organic solvent, and wherein the first and second benefit agents are different; a plurality of a third type of microcells that do not contain a formulation comprising a benefit agent; wherein each microcell of the pluralities of the first, second, and third types of microcells includes walls and an opening; wherein each microcell of the pluralities of the first and second types of microcells includes a sealing layer spanning the opening; and wherein at least one microcell of the first type of microcells does not have any adjacent microcell of the second type of microcells in the layer of microcells.
 2. The benefit agent delivery system of claim 1, wherein the first organic solvent and the second organic solvent are the same.
 3. The benefit agent delivery system of claim 1, wherein the first organic solvent and the second organic solvent are different.
 4. The benefit agent delivery system of claim 1, wherein each of the first type microcells does not have any adjacent second type of microcells in the layer of microcells.
 5. The benefit agent delivery system of claim 1, wherein the plurality of the third type of microcells does not include a sealing layer spanning the opening.
 6. The benefit agent delivery system of claim 1, wherein the plurality of the first and second types of microcells further comprises an adhesive layer adjacent to the sealing layer.
 7. The benefit agent delivery system of claim 1, wherein at least one of the first type of microcells is separated from the second type of microcells by three or more of the third type of microcells.
 8. The benefit agent delivery system of claim 1, wherein the plurality of the first type of microcells further comprises a first porous diffusion layer adjacent the sealing layer, and the plurality of the second type of microcells further comprises a second porous diffusion layer adjacent to the sealing layer.
 9. The benefit agent delivery system of claim 8, wherein the first porous diffusion layer comprises an acrylate, a methacrylate, a polycarbonate, a polyvinyl alcohol, cellulose, poly(N-isopropylacrylamide) (PNIPAAm), poly(lactic-co-glycolic acid) (PLGA), polyvinylidene chloride, acrylonitrile, amorphous nylon, oriented polyester, terephthalate, polyvinyl chloride, polyethylene, polypropylene, polybutylene, polyisobutylene, or polystyrene.
 10. The benefit agent delivery system of claim 8, wherein the first porous diffusion layer has an average pore size of between 10 nm and 100 μm.
 11. The benefit agent delivery system of claim 1, wherein the benefit agent is a pharmaceutical compound or an aroma compound.
 12. The benefit agent delivery system of claim 1, wherein each of the plurality of the first, second, and third microcells has a volume greater than 100 nL.
 13. The benefit agent delivery system of claim 1, further comprising an encapsulating cover that encapsulates the benefit agent delivery system.
 14. The benefit agent delivery system of claim 6, further comprising a backing layer in contact with the adhesive layer.
 15. The benefit agent delivery system of claim 1, wherein the first formulation additionally includes a thickening agent.
 16. The benefit agent delivery system of claim 8, wherein the first porous diffusion layer has average pore size that is larger than the average pore size of the second porous diffusion layer.
 17. A benefit agent delivery system including a layer of microcells, the layer of microcells comprising: a plurality of a first type of microcells filled with a first formulation comprising a first benefit agent and a carrier, wherein the carrier of the first formulation comprises a first organic solvent; a plurality of a third type of microcells filled with a third formulation that does not contain any benefit agent; wherein each microcell of the first and third types includes walls and an opening; wherein each microcell of the first and third types includes a sealing layer spanning the opening; wherein the benefit agent delivery system comprises one or more segments of the first type of microcells, wherein each segment of the first type of microcells exclusively comprises only microcells of the first type of microcells, and wherein all the microcells of the first type of microcells that are adjacent to any other microcell of the segment of the first type of microcells are members of the same segment; and wherein the periphery of at least one segment of the first type of microcells is surrounded by microcells of the third type of microcells.
 18. The benefit agent delivery system of claim 17, further comprising a plurality of a second type of microcells filled with a second formulation comprising a second benefit agent and a carrier, wherein the carrier of the second formulation comprises a second organic solvent, wherein each microcell of the second type includes walls and an opening; wherein each microcell of the second type includes a sealing layer spanning the opening; wherein the benefit agent delivery system comprises one or more segments of the second type of microcells, wherein each segment of the second type of microcells exclusively comprises only microcells of the second type of microcells, and all the microcells of the second type of microcells that are adjacent to any other microcell of the segment of the second type of microcells are members of the same segment; wherein the periphery of at least one segment of the second type of microcells is surrounded by microcells of the third type of microcells; and wherein each of the first type microcells does not have any adjacent second type of microcells in the layer of microcells.
 19. The benefit agent delivery system of claim 18, wherein each of the plurality of the first, second, and third types of microcells further comprises a porous diffusion layer adjacent to the sealing layer.
 20. The benefit agent delivery system of claim 19, wherein each of the plurality of the first, second, and third types of microcells further comprises an adhesive layer, wherein the porous diffusion layer is disposed between the sealing layer and the adhesive layer. 